EGU2020-10124
https://doi.org/10.5194/egusphere-egu2020-10124
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Modes of response of the subsurface western South Atlantic to the last glacial Dansgaard-Oeschger cycles

Thiago Santos1, João Ballalai1, Daniel Franco2, Rômulo Oliveira2, Douglas Lessa1, Igor Venancio3, Cristiano Chiessi4, Henning Kuhnert5, Heather Johnstone5, and Ana Luiza Albuquerque1
Thiago Santos et al.
  • 1Programa de Geociências (Geoquímica), Universidade Federal Fluminense, Niterói, Brazil (thiagopds@id.uff.br)
  • 2Coordenação de Geofísica, Observatório Nacional, Rio de Janeiro, Brazil
  • 3Center for Weather Forecasting and Climate Studies (CPTEC), National Institute for Space Research (INPE), Cachoeira Paulista, Brazil
  • 4Escola de Artes, Ciências e Humanidades, Universidade de São Paulo, São Paulo, Brazil
  • 5MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

The last glacial was an interval characterized by a sequence of abrupt millennial-scale events well documented mainly from the Greenland and Antarctica ice-cores. Although the triggers are not fully understood, most of the works agree that they occurred in consonance with oscillations in the strength of the Atlantic Meridional Overturning Circulation (AMOC). Paleoceanographic reconstructions have shown that cold millennial-scale stadials were accompanied by high temperatures in the subsurface to intermediate waters of the Atlantic Ocean that may have acted in both the basal melting of ice-sheets and in the rapid atmospheric warming during the onset of warm interstadials. Assuming that recent transient models indicated an accentuated response of the subsurface western South Atlantic to the millennial-scale disturbances, here we present a paleoceanographic reconstruction in this area based on the deep-dwelling planktic foraminifer Globorotalia inflata. Our high-resolution oxygen isotope (d18O) presents a sequence of millennial-scale variability that strongly resembles the structure of the Greenland Dansgaard-Oeschger cycles, mainly during Marine Isotope Stage (MIS) 5. On the other hand, during MIS 3, this millennial-scale feature is absent or weakly represented. Cross-spectral analyzes indicate a meaningful north-to-south forcing over the western South Atlantic subsurface during early-glacial. Mg/Ca-derived temperature and ice-volume free seawater d18O (d18OIVF-SW) executed for the MIS 5 interval demonstrated that the subsurface western South Atlantic was warmer and saltier (colder and fresher) during early glacial stadial (interstadials). We hypothesized that a wide reorganization of the northward heat transport throughout the last glacial occurred, in which regions so far south as 24 ºS worked as prominent heat reservoirs in periods of weakened AMOC during MIS 5 but not necessarily during MIS 3. Our data suggest that future impacts over the AMOC along the Brazilian margin will likely be recognized in the subsurface layers of the western South Atlantic.

How to cite: Santos, T., Ballalai, J., Franco, D., Oliveira, R., Lessa, D., Venancio, I., Chiessi, C., Kuhnert, H., Johnstone, H., and Albuquerque, A. L.: Modes of response of the subsurface western South Atlantic to the last glacial Dansgaard-Oeschger cycles , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10124, https://doi.org/10.5194/egusphere-egu2020-10124, 2020